How might mountain-building processes differ on terrestrial planets orbiting stars other than the Sun? The rapidly evolving field of exoplanet detection and characterisation is bringing these questions into the realm of geophysical modelling studies. In the case of homogeneous rock and simplified geometry — without considering the effect of elasticity of the plates, surface temperature, and volatile inventory — planet size will play a large part in determining maximum attainable mountain height through gravitational forces alone.
However, during uplift and contraction the critical slope of a mountain flank is a product of surface gravity and the strength of the rock. Several factors affect rock strength, but temperature, fluid pore pressure, and hydration are key determinants, and may vary considerably between terrestrial planets. It is not yet clear as to whether different modes of tectonic evolution, e.g. episodic or ‘stagnant lid’ regimes as opposed to plate tectonics, will be dominant on terrestrial exoplanets nor what might control the onset of these modes.
We anticipate that mountain height and slope will, to first order, affect physical and chemical weathering processes by exposing more (or less) weatherable material to the atmosphere, as well as affecting the efficiency of delivering weathered material to the oceans. Given that the amount of weatherable material at high altitudes is likely to have a significant effect on the operation of the carbonate-silicate cycle and its ability to regulate CO2 and climate, the relationship between planet size, mountain height, and terrestrial weathering is one that warrants further investigation.
Policy Impact of Research:
The project investigates effects of land/ocean/atmosphere connections on long-term climate on the planetary scale. Modelling techniques developed for this project (use of 1-D, 3-D climate models, instrument simulators) are suitable for quantifying anthropogenic impacts on Earth, as well as for informing, prioritising, and refining future observational campaigns for exoplanet characterisation.